He's saying so right now in the monologue, that since the 17th Amendment was passed the Senate has stopped functioning for the purpose for which the constitution had designed it.
It is indeed useless.
Popular election of senators made the US Senate a "Super House", which was a kind of a power grab away from the US House where popular power was distributed among many.
Now popular power is concentrated among few.
The Senate still acts as a barrier to the House's energy, but it no longer reflects the direct will of the state legislatures which once appointed them.
